Effect of interpass temperature on residual stresses in multipass welds produced using low transformation temperature filler alloy

Abstract

Weld filler alloys that exploit transformation plasticity through low austenite to martensite transformation temperatures offer an effective method of reducing residual stresses in strong steel welds. However, in multipass welds, the heat input from later weld passes may be insufficient to retransform prior welding passes, leading to the accumulation of thermally induced strains and elevated residual stresses. In this work, the residual stress distributions produced around arc welds fabricated with a martensitic weld filler alloy that transforms at a low temperature have been studied as a function of the number of passes deposited and the interpass temperature. It is found that when the interpass temperature is above the transformation temperature of the weld metal, the entire multipass weld transforms as a single entity, thus permitting the optimum exploitation of the transformation plasticity. In contrast, the deposition of new metal with a relatively low interpass temperature leads to increased residual stresses in the underlying layers, reducing or eliminating the beneficial stress states previously created.

Keywords:

• Transformation induced plasticity
• Martensitic weld metal
• Residual stress
• Welding phase transformation

We are grateful to ESAB AB for sponsoring this research. We also acknowledge the support of Dr I. Lonardelli for his participation in the experimental team. This work is based upon experiments performed on the ENGIN-X instrument at ISIS, Rutherford Appleton Laboratory, Didcot, UK, and the STRESS-SPEC instrument operated by FRM II at the Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany.